#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    ifstream fin("nrtri.in");
    fin >> n;

    vector<int> v(n);
    for (int i = 0; i < n; i++)
        fin >> v[i];

    sort(v.begin(), v.end());

    long long cnt = 0;

    for (int k = n-1; k >= 2; k--) {

        int i = 0;
        int j = k-1;

        while (i < j) {

            if (v[i] + v[j] >= v[k]) {

                cnt += j - i;
                j--;
            }
            else
                i++;
        }
    }
    ofstream fout("nrtri.out");
    fout << cnt;
}